FW-517 & FW-536: private directive issues - #27743

…er (#27743)

This refactoring moves code around between a few of the ngtsc subpackages,
with the goal of having a more logical package structure. Additional
interfaces are also introduced where they make sense.

The 'metadata' package formerly contained both the partial evaluator,
the TypeScriptReflectionHost as well as some other reflection functions,
and the Reference interface and various implementations. This package
was split into 3 parts.

The partial evaluator now has its own package 'partial_evaluator', and
exists behind an interface PartialEvaluator instead of a top-level
function. In the future this will be useful for reducing churn as the
partial evaluator becomes more complicated.

The TypeScriptReflectionHost and other miscellaneous functions have moved
into a new 'reflection' package. The former 'host' package which contained
the ReflectionHost interface and associated types was also merged into this
new 'reflection' package.

Finally, the Reference APIs were moved to the 'imports' package, which will
consolidate all import-related logic in ngtsc.

PR Close #27743

#27743)

Upcoming work to implement import resolution will change the dependencies
of some higher-level classes in ngtsc & ngcc. This necessitates changes in
how these classes are created and the lifecycle of the ts.Program in ngtsc
& ngcc.

To avoid complicating the implementation work with refactoring as a result
of the new dependencies, the refactoring is performed in this commit as a
separate prepatory step.

In ngtsc, the testing harness is modified to allow easier access to some
aspects of the ts.Program.

In ngcc, the main change is that the DecorationAnalyzer is created with the
ts.Program as a constructor parameter. This is not a lifecycle change, as
it was previously created with the ts.TypeChecker which is derived from the
ts.Program anyways. This change requires some reorganization in ngcc to
accommodate, especially in testing harnesses where DecorationAnalyzer is
created manually in a number of specs.

PR Close #27743

…es (#27743)

@angular/forms declares several directives and a module which are not
exported from the package via the entrypoint, either intentionally or as a
historical accident.

Ivy's locality principle necessitates that directives used in user code be
importable from the package which defines them. This requires these forms
directives to be exported.

Several directives which define ControlValueAccessors are exported:

* NumberValueAccessor
* RangeValueAccessor

A few more directives and a module are exported privately (with a ɵ prefix):

* NgNoValidate
* NgSelectMultipleOption
* InternalFormsSharedModule

PR Close #27743

…int (#27743)

This commit adds tracking of modules, directives, and pipes which are made
visible to consumers through NgModules exported from the package entrypoint.
ngtsc will now produce a diagnostic if such classes are not themselves
exported via the entrypoint (as this is a requirement for downstream
consumers to use them with Ivy).

To accomplish this, a graph of references is created and populated via the
ReferencesRegistry. Symbols exported via the package entrypoint are compared
against the graph to determine if any publicly visible symbols are not
properly exported. Diagnostics are produced for each one which also show the
path by which they become visible.

This commit also introduces a diagnostic (instead of a hard compiler crash)
if an entrypoint file cannot be correctly determined.

PR Close #27743

Previously, ngtsc would assume that a given directive/pipe being imported
from an external package was importable using the same name by which it
was declared. This isn't always true; sometimes a package will export a
directive under a different name. For example, Angular frequently prefixes
directive names with the 'ɵ' character to indicate that they're part of
the package's private API, and not for public consumption.

This commit introduces the TsReferenceResolver class which, given a
declaration to import and a module name to import it from, can determine
the exported name of the declared class within the module. This allows
ngtsc to pick the correct name by which to import the class instead of
making assumptions about how it was exported.

This resolver is used to select a correct symbol name when creating an
AbsoluteReference.

FW-517 #resolve
FW-536 #resolve

PR Close #27743